Multiple windows flickering: really annoying bug

Does anybody is also facing the following bug? I use to have 2, or even 3 Vivaldi windows opened, each with a few tabs. It usually works fine until I hibernate my PC. But once I resume it, the different Vivaldi windows start flickering without ending. As if, each was willing to get the focus. The only workaround I found so far, is to kill all Vivaldi processes, and then restart the browser. But this is really, really annoying. I'll file a bug about this, but wanted to know if somebody else was also facing it. TIA

The same sometimes occurs for me. Windows 7 x64, Vivaldi 1.0.365.3 64-bit, but several previous versions also exhibited this issue.

I also have several windows open, with multiple tabs. I do not hibernate my computer, and the flickering may begin spontaneously. Today it happened when I switched to another Vivaldi window via the taskbar button (I have disabled grouping of taskbar buttons).

I had three Vivaldi windows open, one of them was active, and I clicked another Vivaldi window's taskbar button. At first, the formerly active and the newly activated Vivaldi windows started flickering (repeatedly activated one after another at a very high rate). When I tried to switch to the third Vivaldi window, it also began flickering together with other two.

When this happens, it is possible to drag the affected windows around, switch tabs and close windows using the close button; but menu commands don't work because an opened drop-down menu gets immediately closed when another window activates. So I have to close all windows one by one and then launch Vivaldi again.

This happens rather rarely for me, but I will be happy to help with any debugging, memory dump or system information the next time it occurs.

Also noticed heavy flickering on plasma ALL THE TIME so I switched to gnome and the issue was smaller, mostly limited to sites where video was played. Went back to plasma and turned on system window decoration (transparent one) and the problem is gone. Not on gnome however, turning system window decoration did actually nothing… in this DE, windows decoration was not applied and flickering was present on videos pages.

So I guess the issue is with composer and windows decoration. Chrome with own window decoration has no such problem. Also I can turn on firefox extension that gets rids of system window decoration and uses own (or lack of it), so it would look like on windows and there is also no problem. Only vivaldi has such issue so I guess it can be fixed somehow.

I like to turn off window decoration because it takes space and does nothing, but at current stage I can't.